This invention relates generally to communication between physical objects, communication and radio systems, radio frequency for item and inventory identification, tracking and management; and more particularly to methods and means of connecting radio circuits and devices to external radiation elements so as to propagate their radio waves.
As the limits of miniaturization in electronic devices are yet to be discovered, the sizes of some other elements in electronics remain constrained by the rules of physics and cannot match the miniaturization exhibited in ICs (Integrated Circuits). A good example of this mismatch in miniaturization is in Radio Frequency Identification (RFID) tags where the whole electric circuit including the memory, controller, radio frequency links, etc. can be implemented in a miniaturized IC, the size of a grain of salt. However, the radiation elements (antennas) needed to radiate the information to the outside world remain relatively large. This mismatch in miniaturization means that extremely small IC pads are to be connected to relatively much larger antennas. That is, the assembly accuracy is dictated by the IC pad geometry which in turn results in the requirement for high placement accuracy and subsequently high cost of assembly.
An important source of performance degradation in small signal CMOS (Complementary Metal Oxide Semiconductor) ICs is their need for protection against ESD (Electrostatic Discharge). The circuitry needed for ESD protection has an undesirable performance impact on an ultra low power radio and in particular on the power recovery frontend of a RFID chip. This is also true for many high data rate ICs for wireless standards to the extent that in some cases ESD is eliminated altogether from critical signals rendering the system vulnerable to discharge effects. Using an indirect non-conductive connection such as the coupling mechanism suggested by this invention, between the antenna and the chip mitigates the need for ESD protection.
Furthermore, many popular conductive materials used to connect ICs to antennas exhibit varying performance in different circumstances, such as changes in humidity. Coupling media (often bond-wires) tend to result in non-predictable or performance degrading characteristics especially for high frequency applications where the inductance of the coupler becomes an important factor. The coupling mechanism suggested by this invention makes the coupling performance insensitive to any such changes.
Normally, it is very difficult to massively probe and test whole wafers while individual dice are still on them. Such a procedure, if possible, would yield significant speed and economic advantages in the testing process. One major motivation for this invention is to enable on-wafer testing of the dice directly before attaching to any external substrates.